The field of the invention is electrical switches, or operator interface devices, and the use of electrical switches, or operator interface devices, in a variety of applications, especially in non-automotive vehicles.
Vehicles are used in many applications in today's world. The many different applications call for vehicles with a variety of capabilities. Non-automotive vehicles may include commercial trucks, tractors, farm equipment, utility vehicles, recreational vehicles, motor homes, buses, and so forth. Typically, every vehicle has a multitude of electrically controlled sub-systems. Examples of common sub-systems include exterior lighting, interior lighting, entertainment systems, heating and air conditioning. Additionally, the vehicle may have more specialized sub-systems such as lifts, pumps, mowers, harvesters, shovels, etc. Each of these sub-systems has some requirement for operator input.
The operator input may be as simple as on/off, or the operator may be required to adjust a value to a particular level. Traditionally, operator input devices for these functions have been rocker switches, toggle switches, push buttons, rotary knobs, and slide actuators. Each of these devices incorporates electrical switch contacts or resistance elements with wiping contacts. Further, each may be individually mounted and wired.
The number and arrangement of individual switches, knobs, and other user input or interface devices in a vehicle depends on many factors. For instance, standard sub-systems may be included on one model of a vehicle but not on other models from the same manufacturer. Further, some sub-systems may be included as optional equipment only, depending on customer requirements. Finally, a manufacturer may also offer optional equipment to be installed after the vehicle is shipped from the factory. All of this variety contributes to complexity in operator panel layout and wiring.
Each different type of input device may require a different type of mounting, termination, or wiring. In vehicles with many different options, there may be an extraordinary number of input devices and mounts. Each one requires connections to a certain number of wires or cables, and configuring the hardware and cables alone requires extensive customization of each vehicle and each option available for the vehicles. It is often impossible to incorporate all variations into the factory wiring harness. Therefore, the time and expense of engineering, mounting, and wiring operator interface panels is a significant part of the total vehicle cost.
Control networks have been proposed as a way to simplify vehicle wiring. A control network allows many input and output devices to share a small number of wires. With an appropriate communications protocol, devices may be added or removed without additional wiring. It is possible to add network communication capability to conventional operator input devices. However, there are drawbacks. A network interface is a microcontroller-based circuit. The microcontroller receives signals from operator input devices and communicates input status on the control network. The signals that are controlled by user input devices are low energy (i.e., very low current and low voltage). Switches that were designed for high current loads may be unreliable when applied in low energy circuits. Contaminants or moisture on the contacts present high impedance to current flow, resulting in poor switch performance. Switches with gold contacts and robust sealing are often employed to assure reliable operation.
The cost to add a network interface to each operator input device could easily exceed the cost of the device itself. Also, gold contacts and sealing add cost to each switch. Thus, adding a network interface to each device would simplify the vehicle wiring, but cost would increase dramatically. A less costly approach is to add a network interface for a complete operator interface panel. Using traditional operator input devices, this approach still is limited by the needs of particular wiring arrangements for each device.
Further, every electrical contact or connection is a potential point of failure. The more electrically active devices there are in the operator interface, the greater the potential for failure. What is needed is a way for many operator input devices to be arranged in a single panel with a greatly reduced number of electrical contacts, connections, and active devices. The solution should also allow the number, type, and arrangement of individual devices to be changed without significant costs for engineering or manufacturing. What is needed is a way to mount several types of switches in a common mount that could used for a great many applications.